Oxygen bleaching agents have become increasingly popular in recent years in household and personal care products to facilitate stain and soil removal. Bleaches are particularly desirable for their stain-removing, dingy fabric cleanup, whitening and sanitization properties, as well as for dye transfer inhibition. Oxygen bleaching agents have found particular acceptance in laundry products such as detergents, in automatic dishwashing products and in hard surface cleansers. Oxygen bleaching agents, however, are somewhat limited in their effectiveness. Some frequently encountered disadvantages include color damage on fabrics and damage to laundry appliances. In addition, oxygen bleaching agents tend to be extremely temperature rate dependent. Thus, the colder the solution in which they are employed, the less effective the bleaching action. Temperatures in excess of 60° C. are typically required for effectiveness of an oxygen bleaching agent in solution.
To solve the aforementioned temperature rate dependency, a class of compounds known as “bleach activators” has been developed. Bleach activators, typically perhydrolyzable acyl compounds having a leaving group such as oxybenzenesulfonate, react with the active oxygen group, typically hydrogen peroxide or its anion, to form a more effective peroxyacid oxidant. It is the peroxyacid compound which then oxidizes the stained or soiled substrate material. However, bleach activators are also somewhat temperature dependent. Bleach activators are more effective at warm water temperatures of from about 40° C. to about 60° C. In water temperatures of less than about 40° C., the peroxyacid compound loses some of its bleaching effectiveness.
Attempts have been made as disclosed in U.S. Pat. Nos. 5,360,568, 5,360,569 and 5,370,826 all to Madison et al. to develop a bleach system which is effective in lower temperature water conditions. However, the dihydroisoquinolinium bleach boosters disclosed in these references, when combined with peroxygen compounds, undergo undesired decomposition, particularly when in the presence of wash solution components.
U.S. Pat. Nos. 5,576,282 and 5,817,614 both to Miracle et al. disclose additional attempts at developing a bleach system comprising organic catalysts which is effective in lower temperature water conditions and is safe on colors.
However, the prior art has failed to teach or disclose the delayed (controlled) addition of formulation components, such as organic catalysts, in accordance with the present invention.
In light of the foregoing, researchers have been pursuing a method to mitigate (or control) the decomposition of the organic catalyst, particularly prior to contact with the oxidizable stain.
Accordingly, the need remains for an effective method to deliver organic catalysts and compositions containing organic catalysts which provide effective bleaching even in lower water temperatures, provides improved stability toward unwanted organic catalyst decomposition, and maximizes peracid performance early in the wash cycle.